Lymphocyte activation markers CD69 and HLA-DR were studied in metastatic breast and ovarian cancer patients who received active specific immunotherapy (ASI) using cancer vaccines containing the synthetic tumor-associated antigen sialyl-Tn or the Thomsen-Friedenreich antigen conjugated to KLH plus DETOX adjuvant. Breast cancer patients who showed prolonged survival following ASI had lower numbers of total CD69+ and CD4+CD69+ cells prior to ASI compared to patients who died. However, following ASI, the surviving patients showed an increase in CD69+ and CD4+CD69+ cells and the deceased patients showed a decrease. A greater than 50% increase in the percentage of cells bearing the activation marker CD69 is associated with an increase in survival in both ovarian and breast cancer patients. In the surviving breast cancer patients there was a significant decrease in the percentage of non-B lymphocyte HLA-DR+ (CD20-HLA-DR+) cells following cyclophosphamide treatment. A strong positive correlation was found between lymphocyte populations CD20- HLA-DR+ and CD8+CD57+, a putative suppressor cell population. Breast cancer patients who showed a greater than median decrease in CD20-HLA-DR+ lymphocytes following cyclophosphamide treatment had a survival advantage over patients who had less than the median decrease in the percent CD20-HLA-DR+ lymphocytes.